Method of fumigating soils and compound for use therein



Patented Dec. 11, 1934 f UN'l-TED STATES-t PATENT I oFFlc z METHOD OF 'FUM'IGATING SOILS AND COM- POUND FOR USE THEREIN Maxwell 0. Johnson, Wahiawa, Territory of Hawaii, assignor to California Packing Corporation, San Francisco, Calif., a corporation of New York No Drawing. Application October 23, 1929,

' Serial No. 401,984 I This invention relate to a method of fumigatnitro compounds effectively destroy or inhibit the ing soils and is particularly concerned with a action of insectary and funigal parasites and cure method of encouraging root growth and prevent all root troubles encountered in badly infected root injuries, wilts, blights and other decay. The soils. By volatile chlorinated nitro compounds,

5 invention also relates to a compound for use in it is desired to include all compounds including 5 fumigating soils, such compound being capable of the radical N02, such as for example, picric acid handling with reasonable safety and of generator trinitrophenol, chloropicrin or other nitro ing a fumigating gas in ,the soil and in the" derivatives of an aliphatic compound, and similar presence of moisture. substances such as dichlor-dinitromethane and A vast number of organisms, animal and vegetetrachlor dinitro 7 ethane. Chlorinated nitro 10 table, live i t e Soil a x t a great influen compounds of j the lower aliphatic series are on s l p uct v n ss- S me of t r an sms particularly desirable because of their volatibility.

aTQeXtremdy minutersuch asfungi and bacteria, Non-volatile compounds are undesirable as they whereas others, for example the larger insects, are apt, t remainin the soil for a sufficient Worms and fungi attain a considerable 5116- length of time? to'cause root injuries instead of 15 m ng the o an sms n u ou o p a y be the beneficial effects observed otherwise. classed nematodes, root fungi such as nephro- It has been found that, chloropicrin ortrimyces, fusarium, etc., and insects such as symm me eth ne is particularly adapted to phylids, varieties of-pycnoscelus, etc. It is exthe t t t of l d it, may be employed tremely difiicult to control or prevent these variwith comparative ease and great efiiciency in 20 ous insects and organisms from attacking the accordance with the methods-described hereinroots of young plants and the plants themselves, afteh 1; only are insects d fungi destroyed particularly as the majority of these organisms or prevented from attacking the plants, but in are extremely resistant to the generally used addition, t growth f plants and roots is greatly insecticides such as for example, hydrocyanic Stimulate The t l t d r wth is; even 25 acid gas, formalin, Bordeaux mixtures, ,oil emulgreater than that obtained by the most care- Sims fully controlled application of fertilizing mate- In addition, he k ow i and insectirials. Chloropicrin'is normally a liquid boiling cides do not afiect all insects and fungi, so that at about 112 degrees mtead of employing repeated treatments with various materials needs liquid chloropicrin, a substantially dry i ture 30 beemployed- Certain. of these insecticides n of picric acid or calcium picrate and bleaching fumigants a injurious to the Plant growth; powder or calcium oxychloride (or other source example, formalin causes bad burning, Bordeaux of m fir acid) may be employed, A dry mixtures injure the plants, copper borate solumixtur f 'picric acid and bleaching powder in 3 5 tions are both injulTious and, have no fungicidal the presence of moisture liberates chloropicrin Valuein accordance with the following reaction:

An object of this invention is td disclose and provide a method of. fumigating soils whereby 2C6Hr0H(N02)3+22CaOCl2=' both insectary and fungidal causes of plant in- 6CChNO2+SCaCOs+13CaClz+3Ca(OH) 2. 40 jury may be controlled or eliminated. v x I An object of this invention is to disclose and A one )Of the oblects of thls Invention 15 to provide a method of stimulating root and plant Y F 9 i a e y' to plantings t partiqularlyin inf t d soils made in soils inf cted with m urlous nematodes, A th r bj tv is t disclose and provide a fungi or insects, it is desirable to introduce the method of'employing nitrated phenols or benzols fumlgatmg a Into the 5011 f to permeate 45 as soil fumigants. the soil to a considerable depth in order to effec- Another object of this inventionis to disclose tiVelY if i k ib 'igj e fievelopmeilt, growth an existand provide a method of em loying volatile chlo- -q e unous P r rinated nitro-compounds as soil fumigants. In of the Volatlle charactel. of chlorlnated Another object is to disclose and provide a nitm ,compounds (such as chloropicrin) which 50 material adapted to be used for soil fumigation. are o b p y means have been p v ded A still further object is to disclose and provide for maintaining the fumigant and plant stimua material adapted to be introduced into soils lant in the soil for an appreciable time.

and liberate chlorinated nitro-compounds therein. In carrying out the invention on Hawaiian pine- Ithas been discovered that volatile chlorinated appleplantations in soils thickly infested with 55 iniurious insects and fungi, the soil is covered with paper mulch or long continuous strips of fairly heavy paper (often impregnated or coated with tar or asphalt), the edges of these strips being covered with loose soil so as to maintain the paper in contact with the soil and prevent its removal by the wind. Liquid chloropicrin or an emulsion containing chloropicrin is then,

preferably injected into the soil at spaced intervals by means of a nozzle inserted through the mulch after the mulclrhas been laid, or immediately prior to the application of the mulch.

chloropicrin thus injected vaporizes toa certain extent beneath the mulch and mrmeates the soil to a considerable depth, the vapors passing both upwardly and horizontally through the soil.

The vapors which pass upwardly through the soil are maintained in contact, with the soil for a considerable period of time, due to the covering of mulch, thereby destroying all surface in sects and fungi.

The penetration of chloropicrin through the soil is remarkable in comparison with results which may have been expected. A heavy soil of the black manganese type which had been well settled by heavy rains and was quite moist and thereby offered maximum .resistance to the penetration of any vapors was employed in one test, in which the burrowing cockroach (Pynoscelus surinamensis) was used as an indicator. These cockroaches were placed in small bottles, the mouths of which were covered'with wire netting. The bottles were buried at different dis- -tances from the point of injection, care being taken not to disturb the soil between the mouth of the bottle and the injection hole, so that a true measure of the horizontal penetration of the vapor through the packed soil would be obtained.

The injection was made. by making a small hole in the soil, one-half inch in diameter and three or four inches deep; a measured amount of chloropicrin was then poured into the hole. Where mulching paper was not used, the injection hole was covered with soil. when paper was used, the injection was made through a. perfora-' tion in the paper and then the perforation was covered.

A preliminary test showed that chloropicrin under the above conditions killed, overnight; through six inches of soil, but not through a foot. A three. day-test was run, with the following results:

7 14 oz. chloropicrin in- M or. chioropicrin in- Distance in soil Depth of meted 1mm from inbottle in gg g Without With pa- Without With pa- 7 P p D D 9 P Inches Inches 12 6 Alivei... Dead Dead... Dead. '12 :12 ..do,.. .llive Alive Do. 18 6 -do Dead.-- do..--. Do.

accelerated. The symphylids, a small-white insect about of an inch long, and a small centipede, similar in appearance but brown in color appear to the worst root gnawing insects infesting the pineapple plantations in Hawaii.- Root cages with glass sides used in "determining the efiect ofchloropicrin showed that these insects were completely destroyed when the soil was fumigated with chloropicrin. The gall-forming nematode, the tylenchus spiralis nematode, and a root-hair fungus (nephromyces) as well as fusarium fungi'and others are substantially completely eliminated. The stimulating action on the beneficial soil bacteria and root growth is remarkable in comparison with plantings in the same but untreated soil.

The remarkable growth stimulation obtained by'liberating chloropicrin beneath the surface of the soil is evidenced by the following comparative weights of pineapple plants in soil treated with chloropicrin. In untreated soil, the average airdry weight of pineapple plants is found to be 361 grams for the shoots and 9.8 grams for the roots. Plantings made in a parallel series of the same soil treated with 2 grams. of chloropicrin per cubic foot of soil produced shoots weighing 581 grams and, roots weighing 17.3 grams. In other words, ,the shoots in treated soil showed an increase, of 161% whereas the roots showed an increase of 176%. This very remarkable growth appears to be correlated with the ammonia nitrogen content of the soil. The ammonianitrogen content of untreated soil ,14 days after planting was 28 parts per million. Soil treated with 2 grams of chloropicrin showed 7'? parts per million, an increase of 282%. 28 days after planting, the untreated soil contained only 17 parts per million of ammonia nitrogen whereas the treated soil contained 69 parts per million. In this connection, attention is called to the fact that during the last two weeks of this period (between the 14 and 28 day periods) a decrease of 40% in ammonia nitrogen content occurred in the untreated soil whereas'but a 10% de: crease occurred in the treated soil. A

chloropicrin is preferably injected into the soil prior to plantingfin liquid state from cylinders made of an anti-corrosive metal such as monel, and the operators should preferably be provided with gas masks- In order to facilitate the fumigation ofsoils, 9. dry mixture of picric acid or a salt of picric acid (such as calcium picrate, sodium picrate, etc), and bleaching powder or other chlorinating agent may be employed, the mixture containing for example ten parts or more, by weight, of bleaching powder to one part} by weight, of dry picric acid. The dry mixture may then be placed into the soil which it is desired to fumigate and covered. The natural moisture of the soil together with rainwater, etc., acting upon the mixture of picric acid and bleaching powder causes the generation of. chloropicrin and thereby liberates the fumigant within the soil over a protracted period of time. I

It is to be understood that the invention is not limited to the particular examples specifically stated hereinabove, but includes all the modifications and changes which come within the scope of the disclosures made hereinabove and the appended claims.

I claim:

1. A method of stimulating plant growth which consists of injecting liquid chloropicrin intoand beneath the surface of the soil, permitting the chloropicrin to vaporize in the soil, and retarding the escape of the chloropiorin vapors from the soil by means of a substantially impervious covering laid upon the surface of the soil substantially above the point of inlection whereby the chloropicrin is rendered available as a plant growth stimulant for a protracted period of time.

- 2. A method of stimulating plant growth which content of the soil is increased and rendered availof the soil by injecting liquid able as a plant growth -period of time.

3. A method of stimulating plant growth which 1-:- iiberating 'chloropicrin beneath the $1 a ace "of the soil, and retarding the upward "escape of the chloropicrin from the soil by means of a tantially impervious covering laid upon the surface of the soil whereby the ammonia nitrogen content of the soil is increased and rentiered available as a plant growth stimulant throughout a zone in the soil adjacent the point of liberation for a protracted period of time.

a. In a method oi stimulating plant growth, the step f increasing the ammonia nitrogencontent of the soil by liberating chloropicrin beneath the surface of the soil,

5. In a method of stimulating p step of increasing the ammonia stimulant for a protracted t growth, the rogen content chloropicrin into z-l-i beneath the surface of the soil.

8. Ina method of stimulating plant growth, the step of injecting a and a bleaching powder into and beneath the surface of the soil.

7. In a method of stimulating plant growth, the step of increasing the ammonia nitrogen content of soils by injecting a mixture of a salt of 'picric acid and bleaching powder into the soil,

mixture of salt of plcric acidfrom the soil by means of a substantially impervious covering laid upon the surface of the soil whereby the chloropicrin is rendered available as a a plant growth stimulant for a protracted period of time. Q I

9. A method of stimulating the growth of pineapple plants, which comprises liberating chloropicrin beneath the surface of the soil and retarding the upward escape of chloropicrin vapors from the soil by means of a substantially impervious covering laid upon the surface of the soil 1 whereby the (min. nitrogen content of the soil is increased and rendered available as a plant growth stimulant throughout the zone in the soil adjacent the point of liberation for a protracted period of time.

. 0. JOHNSON. 

